I am experimenting with Olde Eynsford 2f and 3f and trying charges from 50 gr to 85 gr. What powders and loads have you found to be accurate with lead roundball ?

Olde Eynsford

70 gr. is the accuracy load in both my Lyman and my son's T/C.

Knocks deer down just fine as well.

Each and every gun is different.  Even of the same model.  It can vary with if you're using a 490 or 495 ball and with different thicknesses of patch.  Your powder charge range is about 50-110 grains for a 50 cal.  You have to try different charges until you find the sweet spot, there might even be two, one with light charge and one with heavy.  Try this testing, 25 yards is fine for this.  Try to find what gives you cloverleaf groups at 25 yards.  Don't bother to fine tune your zero until you can get a good group.  If you plan to use this for hunting then adjust your sights for a zero at 50 or 75 yards.  Some people think hitting a pie plate at 50 yards is good but it's not, they don't know what the guns are capable of.

I used 90 grains of 3f Goex in my Lyman Great Plains 50 cal with a true .501 roundball, denim pillow ticking, and actual rendered bear fat as a lube, for my target and hunting load. This load would consistently group aroung 4-5 inches @ 100 yards when shot from sandbags. Plenty accurate for the half dozen or so deer it killed, albeit mostly at 30-70 yard distances.

As has been stated in prior posts EVERY BLACK POWDER GUN will have its own preferred recipes that gives the most accurate results. Your just going to have to suss yours out. And if you change anything, primers, patch material, powder granulation and or lot numbers, you'll need to confirm your groups and zero. That being said, once you find your sweet spot combo, those changes are not likely to drastically change things by a whole lot. BP takes a little more work sometimes but its worth it imho.

My Investarms .50 always liked 95 grains of Goex 2F.